Like anything else, depends on what you want it for. I have a Western Digital USB drive that I use to primarily backup my pictures and financial data. Like other people said, they can, and will, eventually fail. They can also be stolen or burned up when your house catches fire. I also keep a small drive, about 300GB, in my safety deposit box. I bring it home once a quarter and backup everything then back to the bank it goes. It's all the pictures that I do not want to lose. These things are dirt cheap and, if you stick with something like WD, or name brand stuff, they are fairly reliable.
America may be, or not be, at war with Islam. One thing however, is certain. They are at war with America.